1. Field of the Invention
The present invention relates to a sublimation type thermal image transfer image receiving medium capable of receiving a dye from a thermal image transfer recording medium, to produce an image with high resolution using a printer which needs a large quantity of thermal energy, such as a sublimation type thermal image transfer printer.
2. Discussion of Background
A thermal image transfer recording system is carried out in such a manner that a thermal image transfer recording medium which comprises a dye-transfer layer containing a dye and/or pigment is superimposed upon an image receiving medium capable of receiving the dye caused to sublime from the dye-transfer layer of the recording medium or receiving the fused portion of the dye-transfer layer when the thermal image transfer recording medium is heated from the back side thereof. In particular, a sublimation-type thermal image transfer recording system can produce a full-color hard copy with an excellent half tone, so that it is greatly attracting public attention now.
In the conventional image receiving medium for us in the sublimation-type thermal image transfer recording system, a dye-receiving layer is formed on a substrate, which dye-receiving layer comprises a thermoplastic resin such as a polyester resin, which can be readily dyed with a heat-sublimable dye, and a releasant. However, the conventional image receiving medium employing a substrate of a single-layered type, such as a sheet of synthetic paper or a plastic film is easily curled when the thermal energy is applied thereto by using a thermal head in the course of thermal image transfer recording. As a result, the transporting performance of the image-receiving medium becomes unsatisfactory in the thermal image transfer recording apparatus.
To improve the transporting performance of the image-receiving medium in the recording apparatus, a three-layer laminated material prepared by laminating a sheet of synthetic paper, a sheet of cellulose fiber paper and a sheet of synthetic paper is used as a substrate of the image receiving medium as disclosed in Japanese Laid-Open Patent Application 62-198497. The transporting performance of the image receiving medium thus obtained is improved because the curling problem is solved to some extent. However, the curling preventing effect in the aforementioned disclosure is not sufficient in practice when the image receiving medium is used in the latest high-speed thermal image transfer recording apparatus.
There is proposed in Japanese Laid-Open Patent Application 63-107587 an image receiving medium for the purpose of forming a light transmitting original thereon for use with an OHP (overhead projector). This image receiving medium comprises a transparent substrate, a transparent image-receiving layer formed on the substrate and a release sheet such as a sheet of synthetic paper, a sheet of cellulose fiber paper or a synthetic resin sheet with a rough surface, formed on the back side of the substrate, opposite to the image-receiving layer with respect to the substrate. The above-mentioned release sheet can be released from the substrate after an image is thermally transferred to the image receiving medium or before the obtained image is projected using the OHP.
The curling of the above-mentioned image receiving medium can be decreased and the transporting performance thereof is improved due to attachment of the release sheet to the substrate. After the release sheet is peeled from the substrate, however, the curling is still a serious problem. Therefore, when the image-receiving medium is used as an image-receiving film for use with the OHP, handling is inconvenient and the projected image is distorted.
In addition, when the image-receiving layer of the image receiving medium comprises a resin such as vinyl chloride resin, the adhesion between the substrate and the image-receiving layer is poor, so that the image-receiving layer is easily peeled from the substrate.